Controls of mantle potential temperature and lithospheric thickness on magmatism in the North Atlantic Igneous Province.

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Abstract

Modelled primary magma compositions of Palaeocene basalts from the North Atlantic Igneous Province (NAIP) require melting at mantle potential temperatures (TP) in the range 1480-1550°C. Modern lavas from the Icelandic rift-zones required TP~1500°C and those from the rift-flanks TP~1450°C. Secular cooling of the NAIP thermal anomaly was therefore in the order of ~50°C in 61 Ma. There were systematic variations in TP of 50-100°C from centre of the thermal anomaly to its margins at any one time, although limits on the stratigraphical distribution of TP determinations do not rule out thermal pulsing on a timescale of millions of years. Variation in extent of melting at similar TP was controlled by local variability in lithospheric thickness. In the west of the NAIP, lithosphere varied from ~90 km at Disko Island to ~ 65 km at Baffin Island, with similar thickness variations being evident for magmatism in the Faroe Islands, Faroe-Shetland Basin and the British Palaeogene Igneous Province (BPIP). Mean pressure of melting ≥ final pressure of melting and the two values converge for melting columns with a melting interval of < 1.5 GPa, regardless of TP. In particular, the majority of BPIP magmas were mostly generated in the garnet-spinel transition in the upper-mantle. Calculated and observed rare earth element distributions in NAIP lavas are entirely consistent with the melting regimes derived from major element melting models. This allows a calibration of rare earth element fractionation and melting conditions that can be applied to other flood basalt provinces.
Original languageEnglish
Pages (from-to)417-436
Number of pages20
JournalJournal of Petrology
Volume57
Issue number2
DOIs
Publication statusPublished - Feb 2016

Keywords

  • temperature
  • basalt
  • mantle plume
  • partial melting
  • P-T conditions

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